Dxdp Communication - Panasonic KX-DT543-B Service Manual

4.2.4.

DXDP Communication

Function:
This circuit performs the same type of communication as between the DPT and PBX, but a slave DPT for DXDP is connected to
the DXDP port.
In addition, it controls power feeding for a slave DPT.
Circuit Operation:
The data to the slave DPT is output from pins 47 and 48 of IC300 and sent via "Q331C331" and "Q332C337" to JK301.
The data from the slave DPT is sent through "C337R350" and is input to the comparator (pin 22) built in IC300.
The threshold voltage of the comparator is determined by R353, R354 and R355. It is input into pin 21 and 23 of IC300.
Power is controlled to the Slave DPT by means of a constant current circuit Q303 and Q304 as below:
• IC300 pin 20 H: Constant current circuit ON.
• IC300 pin 20 L: Constant current circuit OFF.
• IC300 pin 25 H: 40mA feed (normal supply to Slave DPT).
• IC300 pin 25 L: 20mA feed (initial supply to Slave DPT).
IC300
ASIC1
DDX0
DDX1
DVRH
DDR
DVRL
GPIO3
GPIO4
C313
47
R312
C312
48 R313
VDD3 VDD33
23
22
DG
R350
21
20
DG DG DG
25
VDD33
Q331
DG
C331
R340
3 B2 C2
4
2 E
R341
1 B1 C1
5
DG
DG
1 6
E1 C1
DG
VDD33
2 B1 5
B2
3 C2 4
E2
C333
Q332 C337
DG
C334
DG
DG
R319
R320
PG
R321
PG
9
KX-DT543/KX-DT543-B/KX-DT546/KX-DT546-B
Q330
TO DPT/SLT
L-D
JK301
L303
4
3
2
L304
1
H-D
Q303
PG
5
DG